Message ID | 1366713572-11978-6-git-send-email-dborkman@redhat.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
On Tue, Apr 23, 2013 at 6:39 AM, Daniel Borkmann <dborkman@redhat.com> wrote: > Bring the timestamping section in sync with the implementation. > > Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Acked-by: Willem de Bruijn <willemb@google.com> > --- > Documentation/networking/packet_mmap.txt | 41 +++++++++++++++++++++++++++----- > 1 file changed, 35 insertions(+), 6 deletions(-) > > diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt > index 65efb85..23dd80e 100644 > --- a/Documentation/networking/packet_mmap.txt > +++ b/Documentation/networking/packet_mmap.txt > @@ -1016,10 +1016,11 @@ retry_block: > ------------------------------------------------------------------------------- > > The PACKET_TIMESTAMP setting determines the source of the timestamp in > -the packet meta information. If your NIC is capable of timestamping > -packets in hardware, you can request those hardware timestamps to used. > -Note: you may need to enable the generation of hardware timestamps with > -SIOCSHWTSTAMP. > +the packet meta information for mmap(2)ed RX_RING and TX_RINGs. If your > +NIC is capable of timestamping packets in hardware, you can request those > +hardware timestamps to be used. Note: you may need to enable the generation > +of hardware timestamps with SIOCSHWTSTAMP (see related information from > +Documentation/networking/timestamping.txt). > > PACKET_TIMESTAMP accepts the same integer bit field as > SO_TIMESTAMPING. However, only the SOF_TIMESTAMPING_SYS_HARDWARE > @@ -1031,8 +1032,36 @@ SOF_TIMESTAMPING_RAW_HARDWARE if both bits are set. > req |= SOF_TIMESTAMPING_SYS_HARDWARE; > setsockopt(fd, SOL_PACKET, PACKET_TIMESTAMP, (void *) &req, sizeof(req)) > > -If PACKET_TIMESTAMP is not set, a software timestamp generated inside > -the networking stack is used (the behavior before this setting was added). > +For the mmap(2)ed ring buffers, such timestamps are stored in the > +tpacket{,2,3}_hdr structure's tp_sec and tp_{n,u}sec members. To determine > +what kind of timestamp has been reported, the tp_status field is binary |'ed > +with the following possible bits ... > + > + TP_STATUS_TS_SYS_HARDWARE > + TP_STATUS_TS_RAW_HARDWARE > + TP_STATUS_TS_SOFTWARE > + > +... that are equivalent to its SOF_TIMESTAMPING_* counterparts. For the > +RX_RING, if none of those 3 are set (i.e. PACKET_TIMESTAMP is not set), > +then this means that a software fallback was invoked *within* PF_PACKET's > +processing code (less precise). > + > +Getting timestamps for the TX_RING works as follows: i) fill the ring frames, > +ii) call sendto() e.g. in blocking mode, iii) wait for status of relevant > +frames to be updated resp. the frame handed over to the application, iv) walk > +through the frames to pick up the individual hw/sw timestamps. > + > +Only (!) if transmit timestamping is enabled, then these bits are combined > +with binary | with TP_STATUS_AVAILABLE, so you must check for that in your > +application (e.g. !(tp_status & (TP_STATUS_SEND_REQUEST | TP_STATUS_SENDING)) > +in a first step to see if the frame belongs to the application, and then > +one can extract the type of timestamp in a second step from tp_status)! > + > +If you don't care about them, thus having it disabled, checking for > +TP_STATUS_AVAILABLE resp. TP_STATUS_WRONG_FORMAT is sufficient. If in the > +TX_RING part only TP_STATUS_AVAILABLE is set, then the tp_sec and tp_{n,u}sec > +members do not contain a valid value. For TX_RINGs, by default no timestamp > +is generated! > > See include/linux/net_tstamp.h and Documentation/networking/timestamping > for more information on hardware timestamps. > -- > 1.7.11.7 > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 65efb85..23dd80e 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -1016,10 +1016,11 @@ retry_block: ------------------------------------------------------------------------------- The PACKET_TIMESTAMP setting determines the source of the timestamp in -the packet meta information. If your NIC is capable of timestamping -packets in hardware, you can request those hardware timestamps to used. -Note: you may need to enable the generation of hardware timestamps with -SIOCSHWTSTAMP. +the packet meta information for mmap(2)ed RX_RING and TX_RINGs. If your +NIC is capable of timestamping packets in hardware, you can request those +hardware timestamps to be used. Note: you may need to enable the generation +of hardware timestamps with SIOCSHWTSTAMP (see related information from +Documentation/networking/timestamping.txt). PACKET_TIMESTAMP accepts the same integer bit field as SO_TIMESTAMPING. However, only the SOF_TIMESTAMPING_SYS_HARDWARE @@ -1031,8 +1032,36 @@ SOF_TIMESTAMPING_RAW_HARDWARE if both bits are set. req |= SOF_TIMESTAMPING_SYS_HARDWARE; setsockopt(fd, SOL_PACKET, PACKET_TIMESTAMP, (void *) &req, sizeof(req)) -If PACKET_TIMESTAMP is not set, a software timestamp generated inside -the networking stack is used (the behavior before this setting was added). +For the mmap(2)ed ring buffers, such timestamps are stored in the +tpacket{,2,3}_hdr structure's tp_sec and tp_{n,u}sec members. To determine +what kind of timestamp has been reported, the tp_status field is binary |'ed +with the following possible bits ... + + TP_STATUS_TS_SYS_HARDWARE + TP_STATUS_TS_RAW_HARDWARE + TP_STATUS_TS_SOFTWARE + +... that are equivalent to its SOF_TIMESTAMPING_* counterparts. For the +RX_RING, if none of those 3 are set (i.e. PACKET_TIMESTAMP is not set), +then this means that a software fallback was invoked *within* PF_PACKET's +processing code (less precise). + +Getting timestamps for the TX_RING works as follows: i) fill the ring frames, +ii) call sendto() e.g. in blocking mode, iii) wait for status of relevant +frames to be updated resp. the frame handed over to the application, iv) walk +through the frames to pick up the individual hw/sw timestamps. + +Only (!) if transmit timestamping is enabled, then these bits are combined +with binary | with TP_STATUS_AVAILABLE, so you must check for that in your +application (e.g. !(tp_status & (TP_STATUS_SEND_REQUEST | TP_STATUS_SENDING)) +in a first step to see if the frame belongs to the application, and then +one can extract the type of timestamp in a second step from tp_status)! + +If you don't care about them, thus having it disabled, checking for +TP_STATUS_AVAILABLE resp. TP_STATUS_WRONG_FORMAT is sufficient. If in the +TX_RING part only TP_STATUS_AVAILABLE is set, then the tp_sec and tp_{n,u}sec +members do not contain a valid value. For TX_RINGs, by default no timestamp +is generated! See include/linux/net_tstamp.h and Documentation/networking/timestamping for more information on hardware timestamps.
Bring the timestamping section in sync with the implementation. Signed-off-by: Daniel Borkmann <dborkman@redhat.com> --- Documentation/networking/packet_mmap.txt | 41 +++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 6 deletions(-)